Allow non-object type elements for foreach rules (#3763)

Co-authored-by: Vyankatesh Kudtarkar <vyankateshkd@gmail.com>

pkg/engine/context/context.go

@@ -59,7 +59,7 @@ type Interface interface {
 	AddNamespace(namespace string) error
 
 	// AddElement adds element info to the context
-	AddElement(data map[string]interface{}, index int) error
+	AddElement(data interface{}, index int) error
 
 	// AddImageInfo adds image info to the context
 	AddImageInfo(info kubeutils.ImageInfo) error
@@ -223,7 +223,7 @@ func (ctx *context) AddNamespace(namespace string) error {
 	return addToContext(ctx, namespace, "request", "namespace")
 }
 
-func (ctx *context) AddElement(data map[string]interface{}, index int) error {
+func (ctx *context) AddElement(data interface{}, index int) error {
 	data = map[string]interface{}{
 		"element":      data,
 		"elementIndex": index,

pkg/engine/mutation.go

@@ -215,7 +215,8 @@ func mutateElements(name string, foreach kyverno.ForEachMutation, ctx *PolicyCon
 		ctx.JSONContext.Reset()
 		ctx := ctx.Copy()
 		store.SetForeachElement(i)
-		if err := addElementToContext(ctx, e, i, false); err != nil {
+		falseVar := false
+		if err := addElementToContext(ctx, e, i, &falseVar); err != nil {
 			return mutateError(err, fmt.Sprintf("failed to add element to mutate.foreach[%d].context", i))
 		}
 

pkg/engine/validation.go

@@ -274,12 +274,7 @@ func (v *validator) validateForEach() *response.RuleResponse {
 			continue
 		}
 
-		elementScope := true
-		if foreach.ElementScope != nil {
-			elementScope = *foreach.ElementScope
-		}
-
-		resp, count := v.validateElements(foreach, elements, elementScope)
+		resp, count := v.validateElements(foreach, elements, foreach.ElementScope)
 		if resp.Status != response.RuleStatusPass {
 			return resp
 		}
@@ -294,7 +289,7 @@ func (v *validator) validateForEach() *response.RuleResponse {
 	return ruleResponse(*v.rule, response.Validation, "rule passed", response.RuleStatusPass, nil)
 }
 
-func (v *validator) validateElements(foreach kyverno.ForEachValidation, elements []interface{}, elementScope bool) (*response.RuleResponse, int) {
+func (v *validator) validateElements(foreach kyverno.ForEachValidation, elements []interface{}, elementScope *bool) (*response.RuleResponse, int) {
 	v.ctx.JSONContext.Checkpoint()
 	defer v.ctx.JSONContext.Restore()
 	applyCount := 0
@@ -328,17 +323,34 @@ func (v *validator) validateElements(foreach kyverno.ForEachValidation, elements
 	return ruleResponse(*v.rule, response.Validation, "", response.RuleStatusPass, nil), applyCount
 }
 
-func addElementToContext(ctx *PolicyContext, e interface{}, elementIndex int, elementScope bool) error {
-	data, err := utils.ToMap(e)
+func addElementToContext(ctx *PolicyContext, e interface{}, elementIndex int, elementScope *bool) error {
+	data, err := variables.DocumentToUntyped(e)
 	if err != nil {
 		return err
 	}
 	if err := ctx.JSONContext.AddElement(data, elementIndex); err != nil {
 		return errors.Wrapf(err, "failed to add element (%v) to JSON context", e)
 	}
-	if elementScope {
+	dataMap, ok := data.(map[string]interface{})
+	// We set scoped to true by default if the data is a map
+	// otherwise we do not do element scoped foreach unless the user
+	// has explicitly set it to true
+	scoped := ok
+
+	// If the user has explicitly provided an element scope
+	// we check if data is a map or not. In case it is not a map and the user
+	// has set elementscoped to true, we throw an error.
+	// Otherwise we set the value to what is specified by the user.
+	if elementScope != nil {
+		if *elementScope && !ok {
+			return fmt.Errorf("cannot use elementScope=true foreach rules for elements that are not maps, expected type=map got type=%T", data)
+		}
+		scoped = *elementScope
+	}
+
+	if scoped {
 		u := unstructured.Unstructured{}
-		u.SetUnstructuredContent(data)
+		u.SetUnstructuredContent(dataMap)
 		ctx.Element = u
 	}
 	return nil

pkg/policy/validate.go

@@ -31,9 +31,9 @@ import (
 	"sigs.k8s.io/controller-runtime/pkg/log"
 )
 
-var allowedVariables = regexp.MustCompile(`request\.|serviceAccountName|serviceAccountNamespace|element\.|elementIndex|@|images\.|([a-z_0-9]+\()[^{}]`)
+var allowedVariables = regexp.MustCompile(`request\.|serviceAccountName|serviceAccountNamespace|element|elementIndex|@|images\.|([a-z_0-9]+\()[^{}]`)
 
-var allowedVariablesBackground = regexp.MustCompile(`request\.|element\.|elementIndex|@|images\.|([a-z_0-9]+\()[^{}]`)
+var allowedVariablesBackground = regexp.MustCompile(`request\.|element|elementIndex|@|images\.|([a-z_0-9]+\()[^{}]`)
 
 // wildCardAllowedVariables represents regex for the allowed fields in wildcards
 var wildCardAllowedVariables = regexp.MustCompile(`\{\{\s*(request\.|serviceAccountName|serviceAccountNamespace)[^{}]*\}\}`)

test/cli/test/foreach/kyverno-test.yaml

@@ -3,7 +3,6 @@ policies:
   - policies.yaml
 resources:
   - resources.yaml
-variables: variables.yaml
 results:
   - policy: validate-empty-dir-mountpath
     rule: check-mount-paths
@@ -40,3 +39,18 @@ results:
     resource: test-pod-with-resources-multiple-ctnrs
     kind: Pod
     status: pass
+  - policy: validate-image-list
+    rule: check-image
+    resource: test-pod
+    kind: Pod
+    status: fail
+  - policy: validate-image-list
+    rule: check-image
+    resource: test-pod-ghcr
+    kind: Pod
+    status: fail
+  - policy: validate-image-list-error
+    rule: check-image
+    resource: test-pod-ghcr
+    kind: Pod
+    status: error

test/cli/test/foreach/policies.yaml

@@ -48,3 +48,48 @@ spec:
                  ephemeral-storage: "?*"
                 limits:
                   ephemeral-storage: "?*"
+---
+apiVersion: kyverno.io/v1
+kind: ClusterPolicy
+metadata:
+  name: validate-image-list
+spec:
+  rules:
+  - name: check-image
+    match:
+      resources:
+        kinds:
+          - Pod
+    validate:
+      message: "images must begin with ghcr.io"
+      foreach:
+      - list: "request.object.spec.containers[].image"
+        deny:
+          conditions:
+            all:
+              - key: '{{ element }}'
+                operator: NotEquals
+                value: 'ghcr.io'
+---
+apiVersion: kyverno.io/v1
+kind: ClusterPolicy
+metadata:
+  name: validate-image-list-error
+spec:
+  rules:
+  - name: check-image
+    match:
+      resources:
+        kinds:
+          - Pod
+    validate:
+      message: "images must begin with ghcr.io"
+      foreach:
+      - list: "request.object.spec.containers[].image"
+        elementScope: true
+        deny:
+          conditions:
+            all:
+              - key: '{{ element }}'
+                operator: NotEquals
+                value: 'ghcr.io'

test/cli/test/foreach/resources.yaml

@@ -24,6 +24,30 @@ spec:
 ---
 apiVersion: v1
 kind: Pod
+metadata:
+  name: test-pod-ghcr
+spec:
+  containers:
+    - image: ghcr.io/test-webserver
+      name: test1
+      volumeMounts:
+        - mountPath: /tmp/cache
+          name: cache-volume
+    - image: ghcr.io/test-webserver
+      name: test2
+      volumeMounts:
+        - mountPath: /tmp/cache
+          name: cache-volume
+        - mountPath: /gce
+          name: gce
+  volumes:
+    - name: cache-volume
+      emptyDir: {}
+    - name: gce
+      gcePersistentDisk: {}
+---
+apiVersion: v1
+kind: Pod
 metadata:
   name: test-pod2
 spec: